The Evolution of Steel Targets: Why SR500+ is a Game Changer
SR500+ vs. AR500/AR550: The Future vs the Past!
If you just want the short of it, SR500+ is a purpose-built ballistic steel made from the ground up to withstand bullet impacts whereas AR500/AR550 was made for the mining industry to resist abrasion. SR500+ is much harder than AR500 meaning it pits less and has more impact resistance than AR550 meaning it's less prone to cracking than AR steels at a similar hardness. This gives you the best of both worlds for steel targets you'll be passing down to your grandchildren instead of scrapping after a season!
What is AR500
AR500 is an industry standard material made by a handful of mills that stands for Abrasion Resistant 500 HBW (Brinell Hardness). It was developed for the mining/construction industries for things like wear plates on equipment, cutting edges on plow blades, teeth on buckets etc. Its alloy chemistry was designed to resist abrasion in high wear situations like this and we used it for steel targets because it was the only economical material available for such a niche industry.
What is SR500+
With the expansion of steel targets in popularity we now have access to an affordable performance steel that is purpose built for us to shoot at. SR500+ stands for Shooting Range 500+ HBW and its alloy chemistry was designed specifically to handle the stresses caused by the point impacts of bullets instead of the abrasion of mining.
What makes SR500+ better
Targets fail for two main reasons... pitting (as seen above) & cracking (as seen below). Pitting is commonly caused by small/fast bullets (.22-250, .22 Creed etc.) which can leave deep pits to wear away at the surface of the target and can cause small bits of lead or copper jacket to fly off the target at unpredictable angles. To resist pitting, the target needs to be hard. While both materials have 500 in the name, in practice they are very different. AR500 has an allowable hardness range of 470-530 HBW but in practice, is commonly on the lower half of the spec range. Targets made from AR500 that is below 500 HBW pit significantly worse than from targets made from harder material.
On the flip side, the spec range for SR500+ is 500-590 HBW with a nominal hardness of 545 HBW. Bullets that will take a gouge out of AR500 will barely scratch the much harder SR500+. As seen in the comparison image above and illustrated in the graphic below, the AR500 target demonstrated much lower resistance to pitting compared to the SR500+ target. I would like to point out that the AR500 target shown above is not typically how AR500 performs, but it is how it performs when the hardness dips too low (but still within spec) below 500 HBW.
The worst performance of the SR500+ with steel core 5.56 Green Tip ammunition at 50 yards was still better than the best the AR500 performed with regular lead core .223 fmj's at 100 yards. I would like to note that it is never recommended to shoot green tip 5.56 at steel targets. Even if it doesn't do much of anything to these SR500+ targets, the steel core doesn't fragment like a lead core does and the steel core will ricochet off the target at unpredictable angles. The graphic below is to scale for a 3/8" thick plate showing both the width and depth of each pit as measured with my digital caliper. You may notice that there isn't a pit under the far-left label for .223 fmj at 100 yards, that's because it was so small that it’s not as thick as the lines in the graphic. It truly is just a scratch to it!
If you've made it this far into this snooze fest of an explanation, I'm giving then you may be asking yourself, "What about AR550? Why not just use that instead?" and the answer to that involves a quick explanation of the second type of target failure, cracking. Impact toughness is the measure of a steel’s ability to absorb impacts without cracking and balancing that against hardness is a tricky thing as
they have an inverse relationship. As hardness goes up, impact toughness goes down. As the target becomes more resistant to pitting, it becomes more susceptible to cracking (and vice versa). SR500+, being designed to take bullet
impacts, has a chemistry that was made to retain more impact toughness as it gets harder. We still must abide the laws of physics so a target made from SR500+ that is 550 HBW will have less impact toughness than a much softer target made from AR500 that's only 490 HBW, but the tradeoff is worth it because SR500+ steel resists pitting so much better. Compared to a similar hardness
AR550 target, it will have better impact toughness by using an alloy made for ballistic impacts as opposed to re-purposed mining steel, we get the best of both worlds.
I hope you enjoyed my TED talk! In all seriousness, don't hesitate to call or email me with any questions and I'll do my best to get you taken care of. My contact info is in the header of AtlasTargetWorks.com